Your original school was Okinawan, right? Okinawan pronunciation is NaiFanchi, whereas Japanese is NaiHanchi (capitalized the H and F solely to make the visually stand out). Same as SaiFa (Okinawan) and SaiHa (Japanese), Bassai (Japanese) and Passai (Okinawan), and several others. From what I understand, Okinawa has a different dialect than mainland Japan.
The you get into ichi, ni, san, etc. vs shodan, nidan, sandan, etc., ie Pinan ichi vs Pinan shodan, Heian ichi vs Heian shodan, etc. In actuality they’re the same kata, just different pronunciations and numbering systems. Yes they have variation from school to school too, but for all intents and purposes they’re the same kata.
To muddy the waters even further, you have Funakoshi (Shotokan founder) who outright changed the names of kata to Japanese names to gain Japanese acceptance of them - Kusanku/Kushanku/another variation (allegedly a person’s name) to Kanku (to view the sky); Naihanchi/Naifanchi (person’s name) to Tekki (horse riding), etc.
And people wonder why it’s so hard to document the history of this stuff